Step-by-step drive for timer

ABSTRACT

The continuously driven drive disc carries a drive pawl and a retracting lever on the same pivot. The pawl is biased against the lever by a compressed spring. The lever is held in retractive position by a tension spring. The lever includes a cam which engages a tab (projecting from the timer end plate) to move the lever to an inactive position against the bias of the tension spring while the drive pawl is restrained from following by reason of engagement of a depending finger with a second tab. Continued rotation of the disc clears the finger from the second tab allowing the compressed spring to drive the pawl into engagement with the internal teeth on the timer cam drum thus driving the drum until the lever clears its tab and is retracted by the second (tension) spring. As the lever is retracted it picks up the pawl and retracts the pawl and the drive step is completed. The drive is more economical than the usual stored energy step drive but is more expensive than a creep-type drive. It makes possible variations in steps (degrees and frequency) and even continuous (rapid) drive.

United States Patent [191 Obermann 5] Mar. 27, 1973 STEP-BY-STEP DRIVEFOR TIIVIER [57] ABSTRACT [75] Inventor: George Obermann, Niles, Ill.The continuously driven drive disc carries a drive pawl and a retractinglever on the same pivot. The pawl is [73] Asslgnee' glz z fi of Amenca Mbiased against the lever by a compressed spring. The at lever is held inretractive position by a tension spring. [22] Filed: Oct. 1, 1971 Thelever includes a cam which engages a tab (projecting from the timer endplate) to move the lever to [21] 185527 an inactive position against thebias of the tension spring while the drive pawl is restrained fromfollow- 52] U.S. Cl ..74/112, 74/577 R, 74/575, ing y reason ofengagement of a depending finger 74/577 SF with a second tab. Continuedrotation of the (118C 51 Int. cl. ..G05g 1/00 elem the finger from theeeeehd ehewhg the 58 Field of Search ..74/568, 577,575, 142, 112, e f eephhg hive the R engagement 7 4/1 16 with the internal teeth on thetimer cam drum thus driving the drum until the lever clears its tab andis retracted by the second (tension) spring. As the lever [56]References cued is retracted it picks up the pawl and retracts the pawlUNITED STATES PATENTS and the drive step is completed. The drive is moreeconomical than the usual stored energy step drive but n. is moreexpensive than a creep type driver It makes 3,678,769 7/1972 Holzer....74/568 possible variations in Steps (degrees and frequency) g f andeven continuous (rapid) drive. ems

Primary Examiner-Charles J. Myhr e Assistant Examiner-Wesley S. Ratliff,Jr. Attorney-John W. Michael et al.

3 Claims, 7 Drawing Figures STEP-BY-STEP DRIVE FOR BACKGROUND OF THEINVENTION In the interval timing art there are essentially two types oftimers, the simplest being the creep-type timer where the timing cam isdriven continuously. A drawback to this type of timer is the relativelylong switching time encountered which can cause arcing and burning ofthe contacts. Furthermore, it is difficult, to say the least, to achievesequenced actuation of various switches within a relatively short periodof time. The step-type timer can achieve short switching time and withinthe actual step can achieve sequencing of switches. Of course, thelonger the step the easier the sequencing problem. The step-type timerusually is a stored energy arrangement which is appreciably moreexpensive than the creep-type drive.

SUMMARY OF THE INVENTION The construction described in the Abstractmakes possible a step drive which lies between the creep-type drive andthe stored energy type drive in cost. The present drive makes possiblevariation of the time between impulses without changing the motor speedand without changing the switching time simply by changing the number ofstationary tabs which can be engaged by the drive pawl and lever duringone revolution of the disc. The step size can be varied with thecontrolling factors being the angular degrees between the teeth and thecam bank, the stationary tabs permitting angular engagement of the teethand governed by the fact that the largest step size must be smaller thanany two consecutive small steps. Thus the present drive, while moreeconomical than the stored energy type drive, offers a considerabledegree of design freedom.

DESCRIPTION OF THE DRAWINGS FIG. I is a schematicized plan view showingthe general orientation of the basic parts.

FIG. 2 is a fragmentary, enlarged plan view showing a portion of thedisc, the pawl, positioning lever, and the tabs on the end plate of thetimer.

FIG. 3 is an exploded partial perspective showing the shape of the pawland retracting lever more clearly and illustrating the orientation ofthese parts to an actuating tab.

FIG. 4 is a plan view with parts broken away showing the orientation ofthe parts at the start of a driving step with the retracting lever movedinto inoperative position and the drive pawl retained in the inactiveposition.

FIG. 5 is comparable to FIG. 4 but shows the parts when the drive pawlhas moved into engagement with the ratchet teeth on the inside of thetiming cam drum, three of such teeth being shown.

FIG. 6 is a fragmentary section taken on line 6--6 in FIG. 5.

FIG. 7 is a section taken as indicated by line 7-7 on FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENT The timer drive motor 10 is mountedon the timer end plate 112 with its output gear 114 driving drive disc16 through idler gear 18. The drive disc is rotated continuously but thetiming cam drum 20 is driven intermittently. The cam drum is illustratedin a schematic manner showing one cam actuating switches 22, 24.Obviously in practice a plurality of cams actuate a plurality ofswitches according to a programmed sequence to control the washingmachine components in the prescribed sequence.

Continuously rotating drive disc 16 is provided with a drive pawl 26 anda retracting lever 28 on a common pivot 29 as may be seen' in FIGS. 3and 6. The pawl member has an upstanding pawl 30 and a depending finger32. The pawl is designed to engage ratchet teeth 34 on the inside of theend of the timing cam drum as may be seen particularly in FIGS. 5 and 6.The depending finger is designed to be controlled by the positioning orcontrol tab 38 bent upwardly from the end plate 12 of the timer. InFIGS. 2, 4, and 5 the pawl member 26 is biased by spring 40 compressedbetween the pawl member and abutment 42 on the retracting lever so as tourge the pawl in a counterclockwise direction about pivot 29 to a pointwhen finger 32 butts against the edge of retracting lever 28. Theretracting lever 28 includes a spring anchor 44 on one end permittingthe tensioned spring 46 to urge the lever, pawl and spring assembly in aclockwise direction as viewed in FIGS. 2, 4, and 5. The other end of thespring is anchored on post 48 carried on the drive disc. Finger 32depends from the pawl member 26 between the long arm of lever 28 and theedge of aperture 50 in the drive disc. The bottom of the lever isprovided with a ramp-like projection or cam 52 which depends through theaperture 50 to engage the second tab 54 bent up from the end plate 12.

As the disc rotates from the position shown in FIG. 2, the dependingpawl finger 32 arrives at a position inside tab 38 to prevent movementof the pawl and then cam 52 strikes tab 54 to cam the lever in acounterclockwise direction against the bias of tension spring 46 andcompression spring 40. The pawl member is prevented from following solong as the depending finger 32 engages tab 38. As soon as the fingerclears tab 38, however, the

compressed spring 40 drives the pawl in a counterclockwise direction todrive pawl 30 into engagement with the ratchet 34 and thus pick up theratchet and start turning the cam bank 20. At this time the position inglever is held in its counterclockwise position so as to not interferewith the pawl movement. As soon as the ramp 52 clears tab 54 thetensioned spring 46 is free to pull the lever in a clockwise directionto pick up pawl finger 32 to withdraw the pawl 30 from the ratchetteeth. This completes the step (the length of the step is determined bydegrees of angular rotation between the time of engagement of a pawlwith the ratchet and the time the pawl is withdrawn). The spacingbetween the teeth 34 may be varied so as to vary the angular stepimparted. The limiting factor is that the largest step must be less thanany two consecutive small steps.

If desired, additional pairs of stationary tabs may be located on theend plate so the cam bank may be advanced more than once per revolutionof the drive disc to change the time between impulses without changingmotor speed or switching time.

An additional feature should be pointed out. On the side of the drivedisc adjacent the end plate there may be a peripherally facing camconfiguration such as 56 I claim: l. A timer including a motorcontinuously'driving a drive disc,

a pawl pivotally supported on the disc and urged into driving position,

a retracting lever biased to a position in which it engages said pawland prevents movement of the pawl into driving position while beingmovable to a position in which the pawl can move to its driving positionif not restrained from such movement,

a timing cam including ratchetteeth,

said pawl being engageable with the ratchet teeth in its drivingposition,

first fixed actuating means positioned to be engaged by said lever asthe disc rotates whereby the lever is moved to a position in which it nolonger restrains movement of the drive pawl,

second actuating means initially engaged by the drive pawl to preventthe drive pawl moving to operating position while the positioning leveris moved to a position in which it does not restrain the drive pawl andthen acting to release the drive pawl for movement under its bias intothe driving position, said lever being subsequently disengaged from saidfirst actuating means whereby the bias acting on the lever acts toretract the lever and retract the drive pawl from engagement with theratchet 35 thereby terminatingthe drive step which was initiated byengagement of the pawl with said ratchet.

2. In a timer drive mechanism for imparting step-bystep movement to atiming cam, 1

a ratchet on the timing cam, a continuously driven drive disc,

a pawl pivotally supported on the disc for movement into and out ofengagement with the ratchet and movable only in the direction of advanceof the adjacent ratchet teeth and the associated timing cam,

means "normally retracting the pawl to an inoperative position in whichit'is disengaged from the ratchet,

means for cyclically actuating the pawl into operative engagement withthe ratchet to advance the timingcam a discreet distance comprising astep of the timing cam,

said retracting means being operative at the end of the discreet step toretract the pawl to said inoperative position.

3. A structure according to claim 2 in which said retracting meanscomprises a lever which is operative to engage the pawl and move thepawl to its inoperative position,

spring means biasing the lever to its retracted position, stationarymeans engageable with the lever as it rotates with the disc to move thelever to an inoperative position in which it is unable to restrainmovement of the pawl, springmeans acting on the pawl in a direction toena e the awl with said ratchet, me a s for r estraining movement of thepawl while said lever is being moved to its inoperative position andoperative to release the pawl for rapid movement to its operativeposition, said lever being released from its inoperative position forretum' movement to its operative position under influence of its springbias a discreet number of degrees of rotation of the disc after the pawlhas been moved to its operative position.

1. A timer including a motor continuously driving a drive disc, a pawlpivotally supported on the disc and urged into driving position, aretracting lever biased to a position in which it engages said pawl andprevents movement of the pawl into driving position while being movableto a position in which the pawl can move to its driving position if notrestrained from such movement, a timing cam including ratchet teeth,said pawl being engageable with the ratchet teeth in its drivingposition, first fixed actuating means positioned to be engaged by saidlever as the disc rotates whereby the lever is moved to a position inwhich it no longer restrains movement of the drive pawl, secondactuating means initially engaged by the drive pawl to prevent the drivepawl moving to operating position while the positioning lever is movedto a position in which it does not restrain the drive pawl and thenacting to release the drive pawl for movement under its bias into thedriving position, said lever being subsequently disengaged from saidfirst actuating means whereby the bias acting on the lever acts toretract the lever and retract the drive pawl from engagement with theratchet thereby terminating the drive step which was initiated byengagement of the pawl with said ratchet.
 2. In a timer drive mechanismfor imparting step-by-step movement to a timing cam, a ratchet on thetiming cam, a continuously driven drive disc, a pawl pivotally supportedon the disc for movement into and out of engagement with the ratchet andmovable only in the direction of advance of the adjacent ratchet teethand the associated timing cam, means normally retracting the pawl to aninoperative position in which it is disengaged from the ratchet, meansfor cyclically actuating the pawl into operative engagement with theratchet to advance the timing cam a discreet distance comprising a stepof the timing cam, said retracting means being operative at the end ofthe discreet step to retract the pawl to said inoperative position.
 3. Astructure according to claim 2 in which said retracting means comprisesa lever which is operative to engage the pawl and move the pawl to itsinoperative position, spring means biasing the lever to its retractedposition, stationary means engageable with the lever as it rotates withthe disc to move the lever to an inoperative position in which it isunable to restrain movement of the pawl, spring means acting on the pawlin a direction to engage the pawl with said ratchet, means forrestraining movement of the pawl while said lever is being moved to itsinoperative position and operative to release the pawl for rapidmovement to its operative position, said lever being released from itsinoperative position for return movement to its operative position underinfluence of its spring bias a discreet number of degrees of rotation ofthe disc after the pawl has been moved to its operative position.